What is MRI of the Breast?
Magnetic Resonance Imaging (MRI) is a noninvasive medical test that helps physicians diagnose and treat medical conditions. MR imaging uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. The images can then be examined on a computer monitor, printed or copied to CD. MRI does not use ionizing radiation (x-rays).
Detailed MR images allow physicians to better evaluate various parts of the body and certain diseases that may not be assessed adequately with other imaging methods such as x-ray, ultrasound or CT scans. MRI of the breast offers valuable information about many breast conditions that cannot be obtained by other imaging modalities, such as mammography or ultrasound.
Common Uses of the Procedure
MRI of the breast is not a replacement for mammography or ultrasound imaging, but rather a supplemental tool for detecting and staging breast cancer and other breast abnormalities.
MR imaging of the breast is performed to:
- Assess multiple tumor locations, especially prior to breast conservation surgery
- Identify early breast cancer not detected through other means, especially in women with dense breast tissue and those at high risk for the disease
- Evaluate abnormalities detected by mammography or ultrasound
- Distinguish between scar tissue and recurrent tumors
- Determine whether cancer detected by mammography, ultrasound, or after surgical biopsy has spread further in the breast or into the chest wall
- Assess the effect of chemotherapy
- Provide additional information on a diseased breast to make treatment decisions
- Determine the integrity of breast implants
Without contrast material, an MRI of the breast can show:
- Breast tissue density
- Enlarged ducts
- Leaking or ruptured breast implants
- The presence of enlarged lymph nodes
By comparing breast images taken before and after contrast material injection, an MRI exam can determine:
- If there are breast abnormalities
- Whether an abnormality looks benign (non-cancerous) or malignant (cancerous)
- The size and location of any abnormality that looks malignant
How to Prepare for the MRI
During the exam, you may be asked to wear a gown or you may be allowed to wear your own clothing if it is loose-fitting and has no metal fasteners. Guidelines about eating and drinking before an MRI exam vary with the specific exam and also with the facility. For some types of exams, you will be asked to fast for 8-12 hours. Unless you are told otherwise, you may follow your regular daily routine and take medications as usual.
Some MRI examinations may require the patient to swallow contrast material or receive an injection of contrast into the bloodstream. The radiologist or technologist may ask if you have allergies of any kind, such as allergy to iodine or x-ray contrast material, drugs, food, the environment, or asthma. However, the contrast material used for an MRI exam, called gadolinium, does not contain iodine and is less likely to cause side effects or an allergic reaction.
The radiologist should also know if you have any serious health problems or if you have recently had surgery. Some conditions, such as severe kidney disease, may prevent you from being given contrast material for an MRI.
Women should always inform their physician or technologist if there is any possibility that they are pregnant. MRI has been used for scanning patients since the 1980’s with no reports of any ill effects on pregnant women or their babies. However, because the baby will be in a strong magnetic field, pregnant women should not have this exam unless the potential benefit from the MRI is assumed to outweigh the potential risks.
Jewelry and other accessories should be left at home if possible, or removed prior to the MRI scan. Because they can interfere with the magnetic field of the MRI unit, metal and electronic objects are not allowed in the exam room.
In most cases, an MRI exam is safe for patients with metal implants, except for a few types. People with the following implants cannot be scanned and should not enter the MRI scanning area unless explicitly instructed to do so by a radiologist or technologist who is aware of the presence of any of the following:
- Internal (implanted) defibrillator or pacemaker
- Cochlear (ear) implant
- Some types of clips used on brain aneurysms
You should tell the technologist if you have medical or electronic devices in your body because they may interfere with the exam or potentially pose a risk depending on their nature and the strength of the MRI magnet. Examples include but are not limited to:
- Artificial heart valves
- Implanted drug infusion ports
- Implanted electronic devices, including a cardiac pacemaker
- Artificial limbs or metallic joint prostheses
- Implanted nerve stimulators
- Metal pins, screws, plates, stents or surgical staples
Risks and Benefits
- MRI is a noninvasive imaging technique that does not involve exposure to ionizing radiation.
- MRI has proven valuable in diagnosing a broad range of conditions, including detecting and staging breast cancer, particularly when other imaging studies (mammography, ultrasound, etc.) fail to provide adequate information.
- MRI enables the discovery of abnormalities that might be obscured by bone with other imaging methods.
- The contrast material used in MRI exams is less likely to produce an allergic reaction than the iodine-based materials used for conventional x-rays and CT scanning.
- MRI is growing in popularity as an addition to traditional x-ray mammography in the early diagnosis of breast cancer.
- MRI has been shown to detect small breast lesions that are sometimes missed by mammography.
- MRI can successfully image the dense breast common in younger women, as well as breast implants, both of which are difficult to image using traditional mammography.
- MRI as an addition to mammography has been shown to be useful in evaluating women at high risk for breast cancer.
- If a suspicious lesion is seen with MRI only, MRI can provide guidance for biopsy.
- The MRI examination poses almost no risk to the average patient when appropriate safety guidelines are followed.
- If sedation is used, there are risks of excessive sedation. The technologist or nurse monitors your vital signs to minimize this risk.
- Although the strong magnetic field is not harmful in itself, implanted medical devices that contain metal may malfunction or cause problems during an MRI exam.
- There is a very slight risk of an allergic reaction if contrast material is injected. Such reactions usually are mild and easily controlled by medication. If you experience allergic symptoms, a radiologist or other physician will be available for immediate assistance.
- Nephrogenic systemic fibrosis is currently a recognized, but rare, complication of MRI believed to be caused by the injection of high doses of MRI contrast material in patients with very poor kidney function.